This invention is directed to a process for reducing the sulfur and ash contents of coal.
The United States, with nearly one-half trillion metric tons of coal reserves, has the largest total coal reserves in the world. Increased coal utilization in this country has been hampered by environmental constraints, such as restrictions on sulfur dioxide, nitrogen oxides, and particulate emissions. There is a need for new technology to meet these environmental constraints at costs acceptable to coal users.
Molten caustic can be used to leach ash and sulfur from coals as described in aforementioned U.S. Pat. Application Ser. No. 486,276 filed on Mar. 10, 1983 now U.S. Pat. No. 4,545,891 by Robert Meyers et al. However, until now there has been no known method for recycling substantially all of the caustic used in the process. Cost and environmental considerations require reuse, rather than disposal, of the used caustic. Therefore, there is a need for a process using molten caustic that effectively removes sulfur and mineral matter from coal, and that also enables the caustic and acid cleaning solutions to be recovered for reuse in the process.